In recent years, in the field of wireless communication networks, technology has become known by which a communication device uses a plurality of antennas with aims such as increasing communication area or cancelling effects of interference. This is sometimes known as diversity technology.
In a wireless network composed of a master station having a plurality of antennas and a plurality of slave stations, when the master station communicates with the plurality of slave stations, it is necessary to select an antenna from among the plurality of antennas to use to communicate data to a slave station.
At such time, when the master station transmits data to a slave station via an antenna, it is preferable that an antenna having a low transmission power is selected. This allows reduced power consumption by the master station, and suppresses the effect of interference for other networks.
Conventionally, as methods related to determining transmission power, methods have been disclosed by which the magnitude of the reception level of data received by the master station is detected, and transmission power is determined based on the reception level (for example, Patent Literature 1).